In the production of silicon wafers for use in the electronics industry, a number of process steps occur. Generally, a cylinder of silica (i.e. a boule) is produced. Wafers are produced by slicing the boule. The application process creates surface defects which are partially removed by a lapping process. Historically, that lapping process has been accomplished through the use of adhesive. The lapping process is considered to be purely a mechanical process of reducing surface defects.
The reason lapping has been traditionally been considered a mechanical process is best appreciated by looking at the purpose for lapping. These purposes are to remove saw damage created by the slicing operation; to maintain accurate wafer thickness; to maintain and create a flatness and parallelism too the wafer; and to prepare the surface for polishing.
A more complete explanation of lapping is shown in the following articles: "Abrasive Technology for Wafer Lapping", by J. A. Dudley, Microelectronic Manufacturing and Testing, March 1986; "How Users Can Optimize Machine Performance in Production Lapping Operations", by Dr. D. Rostoker, Microelectronic Manufacturing and Testing, pgs. 9-10, May 1987; and "Crystallographic Damage to Silicon by Typical Slicing, Lapping, and Polishing Operations" by T. M. Buck and R. L. Meek, NBS Special Publication No. 337, pgs., 419--30.
This lapping process is traditionally followed by a polishing process. The function of polishing is to provide a highly finished surface suitable for use as a "chip" in the electronics industry. Polishing steps include mechanical polishing using fine abrasives and caustic action brought about by elevation of the polishing composition pH.
After polishing the chip is further processed to include the microcircuitry required by the industry.
The lapping slurries themselves have generally been held at a pH close to neutral. This allows lapping machine operators to manually spread lapping slurries of the wafer being treated. Thus a uniform coating of a coating slurry on the wafer surface is brought about. This machine operator practice is universal.
It would be beneficial if a lapping composition or method could be conceived and produced which would improve on lap rate and/or decrease wafer defects that have been engendered by the cutting operations.